SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, Fair Value Measurements (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Fair Value Measurements [Abstract]
Held-to-maturity securities, unrecognized loss	$ 0	$ 0
Amortized premium included in interest income	(160,000)	(673,000)
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, current	48,751,206	51,973,971
Held-to-maturity securities, noncurrent	2,840,191	5,745,974
Recurring [Member] \| Institutional Money Market [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,432,432	3,108,549
Recurring [Member] \| Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		800,000
Investments	3,525,134	1,102,650
Recurring [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,585,000
Investments	42,328,363	51,299,068
Recurring [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	250,000
Investments	5,737,900	5,318,227
Recurring [Member] \| Level 1 [Member] \| Institutional Money Market [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	7,432,432	3,108,549
Recurring [Member] \| Level 1 [Member] \| Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 1 [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,585,000
Investments	0	0
Recurring [Member] \| Level 1 [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	250,000
Investments	5,737,900	5,318,227
Recurring [Member] \| Level 2 [Member] \| Institutional Money Market [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Recurring [Member] \| Level 2 [Member] \| Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		800,000
Investments	3,525,134	1,102,650
Recurring [Member] \| Level 2 [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Investments	42,328,363	51,299,068
Recurring [Member] \| Level 2 [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Investments	0	0
Recurring [Member] \| Level 3 [Member] \| Institutional Money Market [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Recurring [Member] \| Level 3 [Member] \| Municipal Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Investments	0	0
Recurring [Member] \| Level 3 [Member] \| Corporate Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Investments	0	0
Recurring [Member] \| Level 3 [Member] \| Certificates of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Investments	0	0
Municipal Bonds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, current	3,425,134	1,002,650
Held-to-maturity securities, noncurrent	100,000	100,000
Corporate Bonds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, current	41,828,133	48,143,495
Held-to-maturity securities, noncurrent	500,230	3,155,573
Certificates of Deposit [Member]
Schedule of Held-to-maturity Securities [Line Items]
Held-to-maturity securities, current	3,497,939	2,827,826
Held-to-maturity securities, noncurrent	$ 2,239,961	$ 2,490,401

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, not expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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